Various types of transducers have been developed to measure the changes in a magnetic field adjacent a rotating shaft, to provide information regarding different shaft characteristics such as speed, torque and horsepower. It has been known that a driven or loaded shaft is stressed and this causes compression and tension in various portions of the shaft, changing the shaft permeability and correspondingly varying the magnetic flux pattern in the shaft. Earlier descriptions of this phenomenon are found in patents such as U.S. Pat. Nos. 2,912,642 -- Dahle and 3,011,340 -- Dahle. However it has proven difficult to adapt these earlier teachings to an economical, compact transducer for use in modern equipment.
A recent, significant advance has been made in the transducer art, and this is set out and claimed in the U.S. application having Ser. No. 747,577, filed Dec. 6, 1976, entitled "System for Measuring Torque and Speed of Rotating Shaft", in the name of Edwin J. Meixner, which is assigned to the assignee of this invention. Even with this significant forward step, in which the physical size and cost of the transducer itself was greatly reduced, it was necessary to provide a bridge-type inverter or a similar switching arrangement to regulate energization of the transducer primary winding. Such an arrangement normally requires four transistors or switches and thus itself adds to the cost and space requirements of the complete instrument system.
It is therefore a primary object of the present invention to provide a torque and/or speed measuring arrangement which is significantly improved as contrasted to known arrangements.
A more particular object of the invention is the provision of such an arrangement in which the most effective trade-off between the driving circuit and the transducer is provided, to provide increased economy and simplification of the system.